1. Field of the Invention
The present invention relates to image forming apparatuses each of which includes a detachable unit and detachable units that can be attached to and detached from image forming apparatuses.
2. Description of the Related Art
Conventionally, image forming apparatuses have a detachable unit that can be slid along a guide section of an apparatus main body when it is inserted into or withdrawn from the apparatus main body. One example of the detachable unit is a toner cartridge. In general, the detachable unit includes a holder for holding a circuit board (cartridge circuit board), and a terminal board having a contact terminal as a leaf spring is mounted on the apparatus main body. When the detachable unit is inserted into the guide section of the apparatus main body, an electrode terminal of the circuit board held in the holder of the detachable unit comes into contact with the contact terminal.
When the user inserts the detachable unit holding the circuit board in the holder along the guide section into the apparatus main body, the contact terminal in its initial state (non-pressed state) meets a part on the front end side of the holder of the detachable unit and is pushed down. When the insertion is completed, the contact terminal held in the holder is in the pressed state and is kept in contact with the electrode terminal of the circuit board by its elastic restoring force.
When the user draws out the detachable unit holding the circuit board in the holder from the apparatus main body by sliding it along the guide section, the detachable unit held in the holder moves while keeping the electrode terminal of the circuit board in contact with the contact terminal. When the detachable unit moves away from the contact terminal, the contact terminal returns from the pressed state to the initial state by its elastic restoring force. See Patent reference 1, Japanese patent application publication No. 2007-140266.
There is a possibility that a detachable unit which does not hold a circuit board in the holder (for example, a detachable unit before a circuit board is mounted or a detachable unit after a circuit board has been removed) is inserted into the apparatus main body along the guide section. When the user inserts the detachable unit not holding a circuit board in the holder into the apparatus main body along the guide section, the contact terminal in its initial state meets a part of the detachable unit (for example, a frame of the detachable unit) and is temporarily pushed down. However, when the insertion is completed, the contact terminal returns to its initial state by its elastic restoring force, and at least a part of the contact terminal enters into the holder (space where the circuit board would be present) of the detachable unit. If the user withdraws the detachable unit in that state by sliding it along the guide section, at least the part of the contact terminal which has been entering in the holder of the detachable unit would be caught by a part of the detachable unit (for example, a frame of the detachable unit), and the detachable unit would disturb smooth pulling-out of the detachable unit.